Surgery – Instruments – Electrical application
Reexamination Certificate
2001-01-09
2003-05-06
Gibson, Roy D. (Department: 3739)
Surgery
Instruments
Electrical application
C606S041000, C600S381000
Reexamination Certificate
active
06558377
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for filling a target site in a living being with an embolic material to occlude the site; and, more particularly, to an apparatus and method for automatically notifying an operator of the instant the embolic material is detached from a guiding member by electrolytic action.
BACKGROUND OF THE INVENTION
There is an operative treatment of treating vascular malformations such as a cerebral aneurysm, which includes the processes of putting a patient under general anesthesia to craniotomy, exposing the cerebral aneurysm in the patient using an operating microscope and a microsurgical unit, and clipping a cervical portion of the cerebral aneurysm with a particular metallic clip. However, such a treatment suffers from drawbacks that it still involves a considerable hazard and a prolonged operating time, which, in turn, may cause serious sequelae.
In an alternative treatment, a Minimal Invasive Treatment (MIT), which employs a technique disclosed in U.S. Pat. No.5,122,136 issued to Guglielmi et al, and U.S. Pat. Nos.4,884,579 and U.S. Pat. No. 4,739,768 issued to Engelson, is utilizing. The MIT Treatment inserts an embolic material within vascular malformations such as a cerebral aneurysm through the use of a micro catheter and a guiding wire under fluoroscopy to occlude the vascular malformations. In contrast with the craniotomy treatment previously explained, the MIT treatment has merits that it is possible to operate under a slight anesthesia with a short operation time, to thereby minimize sequelae and also lower an operation cost.
An embolic material mainly utilized in the MIT treatment includes a metallic coil. The metallic coil is disclosed in, for example, U.S. Pat. Nos. 5,354,295, 5,669,905 and 6,066,133 and Japanese Patent Nos. 10-057385, 11-047138 and 11-076249. In the following, the metallic coil cited in U.S. Pat. No. 5,669,905 will be described.
FIG. 1
is a pictorial view of a metallic embolic coil used in the conventional MIT treatment.
As shown in
FIG. 1
, a guiding wire assembly
100
typically includes a stainless steel-based guiding wire
1
and a coil-shaped embolic material
8
, the guiding wire
1
being tapered its distal end and the embolic material
8
being connected with the distal end of the guiding wire
1
by a micro welding. The embolic material
8
is made of a radiopaque material including Platinum, Tungsten, Iridium or these alloys, and has welded portions
6
and
7
at its both ends. The welded portions
6
and
7
are made of platinum that acts as a marker under fluoroscopy.
A surface of the guiding wire
1
is coated with an insulating material such as Teflon, with the exception of a proximal end
5
acting as a sacrificial link to be connected with the welded portion
6
of the embolic material
8
. The sacrificial link
5
is made of an electrically conducting material such as stainless steel, which is a portion to be detached from the guiding wire
1
by electrolytic disintegration. The guiding wire
1
is coupled with the welded portion
6
of the embolic material
8
via the sacrificial
5
, which is interposed in a sleeve
2
and a plug
3
with inserted within an internal coil
4
. The internal coil
4
is designed to provide column strength to the guiding wire
1
, without a bad influence for a flexibility of the tapered portion in the guiding wire
1
. As shown in
FIG. 1
, the embolic material
8
has been designed its shape changed into a coil form when it is gradually withdrawn from a micro catheter
7
, to thereby allow the embolic material to adapt to the shape of the vascular malformation.
FIG. 2
is a pictorial view illustrating insertion and detachment processes of the embolic material
8
in the prior art.
Typically, the insertion of the embolic material
8
in a vascular malformation
11
is performed using fluoroscope under local anesthesia. Specifically, as shown in
FIG. 2A
, an operator guides a micro catheter
10
to near neck
12
of the vascular malformation
11
in a living being or a patient. After that, the operator inserts the guiding wire
1
attached the embolic material
8
on its distal end into the micro catheter
10
, and gently push the guiding wire
1
using the fluoroscope at least until the sacrificial link
5
is exposed beyond the distal end of the micro catheter
10
.
In an ensuing step, an electrical loop is formed wherein a positive electrode of a power supply
13
is attached to the proximal end of the guiding wire
1
and a negative electrode is placed in electrical contact with the skin of the patient. Thereafter, the power supply
13
is turned on to allow a DC power with AC superposition to be applied to the embolic material
8
through the sacrificial link
5
of the guiding wire
1
. As a result of the above process, the embolic material
8
is detached from the guiding wire
1
by electrolysis as shown in FIG.
2
B. Next, the guiding wire
1
and the micro catheter
10
are withdrawn from the vascular malformation
11
.
FIG. 3
shows a schematic block diagram of the prior art apparatus of detecting the detachment of the embolic material from the guiding wire.
The prior art apparatus
200
includes a constant current source
16
, a circuit
18
for detecting the detachment of the embolic material and a microprocessor
19
. The constant current source
16
provides a constant current to the patient
17
, which includes an operational amplifier (OP Amp)
16
a
and a DC feedback loop
16
b.
The OP Amp
16
a
will oscillate in approximately 30 kHz at amplitude of several hundred milli-volts due to a lagging error correction signal (out-of-phase feedback). That is, the OP Amp
16
a
provides a DC current with AC superposition. The amplitude of such AC signal is dependent on bandwidth characteristics of the OP Amp
16
a,
AC impedance of the stainless steel and the embolic material
8
, and the patient's body. The DC constant current flowing out of the OP Amp
16
a
flows through the sacrificial link
5
of the guiding wire
1
to the embolic material
8
.
Although the sacrificial link
5
and the embolic material
8
are physically connected in series, immersion of them in an electrolytic solution forms two parallel DC current paths each of that is grounded through the body of the patient
17
. Specifically, by ion flow away from the stainless steel-based link
5
during electrolysis, the DC current with AC superposition flowing between the sacrificial link
5
and the embolic material
8
in the vascular malformations
11
is branched as follows. That is, the majority of the DC current (above 99%) flows through the sacrificial link
5
with the remaining (less 1%) flowing through the embolic material
8
. Thus, if the embolic material
8
is separated from the link
5
and a portion of the sacrificial link
5
remains attached to the guiding wire
1
, the main DC current is fed back to the DC feedback loop
16
b
of the constant current source
16
. The AC current is grounded through the embolic material
8
.
As shown in
FIG. 3
, the DC current with AC superposition is blocked out by a pick-off capacitor (not shown), only the AC signal is fed to the detection circuit
18
for measurement of AC impedance. The detection circuit
18
receives the AC current from the embolic material
8
in the patient
17
to detect whether or not the embolic material
8
is detached. Specifically, the AC current fed to the detection circuit
18
is amplified in an AC signal amplifier
18
a
and is rectified in an AC-DC rectifier
18
b.
Then, the rectified DC signal is amplified in a DC level amplifier
18
c
and sent to the microprocessor
19
, wherein the amplified DC level is representative of the amplitude of the AC voltage of the OP Amp
16
a.
The microprocessor
19
monitors the level of the amplified DC signal every 50 to 200 milliseconds and constantly averages the signal every specific sample. In this manner, if a sudden DC voltage drop is incurred, the microprocessor
19
determines that the embolic material
8
is detac
Kim Yong-Churl
Lee Kyu-Ho
Gibson Roy D.
Lee Kyu-Ho
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